How is sexual reproduction related to gender determination in mammals?

One pair of chromosomes in a human cell is the sex chromosomes. In sexual reproduction, two distinct gametes fuse to form a zygote. The gametes are produced through the process of the meiosis. Each individual gamete only contains one set of chromosomes. So when the male and female gamete fuse, the zygote is diploid, which means it contains two sets of chromosomes.
In humans, the sex chromosomes are either X or Y. The female gametes are X only, while the male can have either X or Y. Therefore, the male sperm cell determines the sex of the individual. If the sperm cell gives an X, the zygote will be a female. If the sperm cell gives a Y, the zygote results in a male.